Open-end spinning apparatus with an aerostatic radial bearing for a spin rotor

ABSTRACT

The invention concerns an open-end spinning apparatus with a spin-rotor ( 1 ), the shaft ( 3 ) of which is supported by an aerostatic, radial bearing ( 5 ) with an air gap ( 9 ) between the bearing assembly and the shaft ( 3 ) and the invention further concerns the aerostatic bearing for this purpose. In accord with the invention, the open-end spinning apparatus is thereby improved, in that the construction material for the bearing surface of the spin-rotor ( 1 ) and/or the bearing surface of the radial bearing ( 5 ) is polyimide or Aramid. In spite of possibly occurring bearing surface contacts, the operating life of the radial bearing is substantially increased by the use of these materials.

DESCRIPTION

[0001] The invention concerns an open-end spinning apparatus with a spin rotor, the shaft of which is radially supported by an aerostatic radial bearing with an air gap between the bearing assembly and the shaft, and the invention further concerns the aerostatic radial bearing for this purpose.

[0002] In the case of a known open-end apparatus (JP 57-27212 B2), the shaft of a spin rotor is respectively held in radial bearings in the areas of its forward and rear ends. . Through the bearing surface of the radial bearing, compressed air is introduced from the rear area thereof through openings in the direction of an air gap situated between the bearing surface of the radial bearing and the bearing surface of the spin rotor. In normal operation, this aerostatic radial bearing makes possible a bearing for a spin rotor which is free from abrasion and friction.

[0003] During operation of open-end spin rotors, however, severe running conditions sometimes occur in such a manner, that an impact between the shaft and the bearing surface happens. These severe running conditions are caused, for example, by imbalance in the spin rotor due to worn drive belts or a jointure in the drive belts. A contacting between the bearing surface of the shaft and the bearing surface of the radial bearing does not necessarily mean a failure of the bearing in service or that the aerostatic radial bearing is immediately unusable because of the said contacting.

[0004] On this account, it is the purpose of the invention to improve an open-end spinning apparatus and the associated radial bearing in such a manner, that the operational life of the radial bearing is substantially increased.

[0005] The purpose is achieved by the features of claim 1.

[0006] In accord with claim 1, in the case of the bearing surface pairing of the bearing surface of the spin rotor and the bearing surface of the radial bearing, at least one of the bearing surfaces is made from a basic material of polyimide or Aramid.

[0007] The use of a high temperature resistant plastic substance in the bearing surface makes possible, upon a tilt of the spin rotor and a touching of the two bearing surfaces, a resilient damping, so that the contact of the rotor shaft on the radial bearings does not lead to such a hard impact of the rotor against the radial bearing, that damage would be caused to the shaft or the bearing. Aramid, in particular Para-Aramid is installed here, for example, either pure or as a fiber composite. The material can be found from commercial sources, for instance, under the market name Kevlar®.

[0008] By the use of the materials polyimide or Aramid, a material pairing is obtained, which has a low friction value, is not temperature sensitive, and the said materials are particularly resistant to mechanical loading. Polyimide or Aramid make available a radial bearing with a high structural and tensile strength for the bearing material. This is an advantage which includes the bearing surfaces. Besides the favorable frictional characteristics, advantageously, also a particularly pronounced ability to withstand mechanical loading is made possible, especially by the resistance to wear of the materials polyimide or Aramid. By this means, the negative effects of mechanical contacts between the bearing surface of the spin rotor and the bearing surface of the radial bearing are essentially lessened.

[0009] These bearing materials, moreover, are in a position to easily resist mechanical loads on the bearing. This is true, not only during operation, but for example, also during the installation of the spin rotor in the radial bearing, in which the air gap between the bearing surfaces allows only a minimal amount of play. By this characteristic, manufacturing errors are reduced and likewise, a contribution to the improvement of the bearing is made. These advantages also become evident, if one or both bearing surfaces are coated with polyimide or Aramid which acts in a manner corresponding to the above.

[0010] Moreover, the said materials are readily workable, whereby the retaining of dimensional tolerances during the manufacturing is assured. This advantageously also provides that the durability of the bearings is improved, since a precise construction in accord with the design specifications can be carried out simply and safely.

[0011] Because the spin rotor is subjected to continuous, extreme loading abrasive wear does occur, in spite of the high resistance of the materials polyimide or Aramid to abrasion and their high degree of wear resistance. Where the use of the said materials in the bearing surfaces of the spin rotor is concerned, on account of this possible wear, it is of advantage to so design the bearing surfaces, that these are removable from the spin rotor and by means of a new coating or by a new bearing installation can be effectively replaced. It is advantageous, when employing these said materials in the bearing surfaces of the radial bearing, to provide an insert, which carries the radial bearing surface. This can be a releasable holding means, serving as an exchangeable component.

[0012] In an advantageous improvement of the invented radial bearing, the polyimide or Aramid material possesses a particularly favorable additive, this being graphite, Teflon®, molybdenum disulfide or a mixture of these.

[0013] Favorably, the portion of this additive lies between 10 and 45%, preferably more than 20%. Thereby, a particularly lower friction factor of the bearing material is achieved, whereby the wear by mechanical contact between the bearing surfaces is again reduced. In regard to the use of favorable basic materials for the bearing surfaces, full recognition is given to Application No. DE 100 14 861.

[0014] By the use of porous materials for bearing surfaces, compressed air can be introduced from the outer circumference of the bearing surface through the porous channels in the material toward the bearing gap between the bearing surfaces. The porous material assures a uniform distribution of the air input without further work-up of the bearing surface material being necessary. For instance, the porous material can be sintered out of polyimide powder with or without the above mentioned additives. Simultaneously, the porous material acts as a throttling device for the application of the air flow into the air gap. In regard to the characteristics of the porous material and the throttle device, recognition is given fully to the Application DE 100 62 106, which is attached to the application in copy form.

[0015] Alternatively, or additionally, to the porous channels in the porous material, in one or both of the bearing surfaces, several borings can be provided. Through these borings the compressed air is introduced from the rear side to the air gap. For uniform distribution of the air in the air gap, the outlet openings of the borings are advantageously axially aligned and so placed that they are also circumferentially offset from one another. If, instead of borings, micro-openings are employed, then the compressed air entering the air gap can be very precisely adjusted. Additionally, the air flow through the micro-openings is minimal, so that upon any axial deviation of the rotor shaft toward the radial bearing, the position-restoring air flow, i.e., the compressed air, cannot be forced back into the inlet openings. This markedly increases the rigidity of the bearing. In regard to the formation of the micro-openings and their distribution over an area, particularly on the bearing surface, recognition is given fully to DE 100 62 106.

[0016] For an additional increase of the operational life of the radial bearing, a material-pairing is employed in the case of the two opposed bearing surfaces, in which the material of the one bearing surface is a hard material, or is coated therewith, so that practically no erosion occurs even by touching against an oppositely situated bearing surface, which contains polyimide or Aramid,.

[0017] In accord with another embodiment, in addition to the radial bearing, an axial bearing is installed to serve as an aerostatic axial bearing with an air gap between a bearing fixture thereon and the shaft end of the spin-rotor. The placement of the bearing surface pairing between the axial bearing apparatus and the shaft end or a confronting device on the shaft end, such as a disk, corresponds to the already described bearing surface pairing between the bearing surface of the spin-rotor and the bearing surface of the radial bearing. In this way, a lubrication-free bearing system is achieved for the axial bearing, and consequently, the operational life of this bearing is also extended. In regard to the placement of the aerostatic axial bearing, full recognition is granted to DE 100 62 106.

[0018] With the aid of the drawings, embodiment examples of the invention are explained in the following. There is shown in:

[0019]FIG. 1 a spin-rotor, which is set in an aerostatic radial bearing and an axial bearing,

[0020]FIG. 2 a detailed presentation of a micro opening in the aerostatic bearing, and

[0021]FIG. 3 a second embodiment of an aerostatic bearing.

[0022]FIG. 1 shows a spin-rotor I of an open-end spinning apparatus with a rotor plate 2 and a shaft 3. The shaft 3 is placed in rotation by a drive belt 4, which tangentially encompasses part of the circumference of the said shaft. The bearing support of the shaft 3, in a radial direction is carried out by two identical radial bearings 5 and the end bearing axial support by an axial bearing 6, which is placed on that end of the shaft 3 which is remote from the rotor plate 2.

[0023] In the case of the embodiment shown in FIG. 1 of the rotor shaft bearing assembly, an axial force, which acts in the direction of axial bearing 6, is countered by the slightly offset run of the drive belt 4 over the shaft 3. In this case, the belt 4 does not aproach the shaft 3 at an angle of 90° to the axis thereof, but at a slightly less angle. If the shaft 3 as seen in FIG. 1 rotates with the upper side turning into the plane of the drawing, and the underside, so to speak, “emerging” therefrom, then the drive belt 4 would be offset (as the drawing is viewed) slightly to the right.

[0024] Alternative to this, the axial force acting in the direction of the axial bearing 6 could be achieved by a slightly conical tapered design of the shaft 3 in the belt 4 contact area. In this case, the conical taper of the shaft in the drawing orientation reduces itself from left to right.

[0025] A shell 8, within a radial bearing housing 7 of the radial bearing 5, is placed so as to circumferentially enclose the shaft 3. On the rear surface of the wall of the shell 8, that is, on that side of the said shell 8 distal from the air gap 9, are constructed compressed air chambers 10 running annularly about the rotor shaft but within the radial bearing housing 7. The compressed air chambers 10 are connected with a (not shown) air channel running in the axial direction, which channel, in turn, is connected to a compressed air source, so that, in the compressed air chambers 10, pressurized air is made available for introduction into the air gap 9.

[0026] In the shell 8 of the bearing housing 7 are placed micro-openings 11, running in a radial direction. These micro-openings 8, because of their small diameter, are shown only as short lines in FIG. 1. In order to assure a uniform inflow of pressurized air into the air gap 9, the micro-openings 11 are offset to one another in an axial direction . For clarity, the micro-openings 11 in FIG. 1 are shown as lying in a cross sectional plane. In fact, these micro-openings are distributed offset from one another also in a circumferential direction along the inner surface of the bearing shell 8.

[0027] The bearing shells 8 are essentially made of polyimide or Aramid, in which friction reducing additives such as Teflon® or graphite have been incorporated. These additives, forming a matrix like structure of the bearing shell 8, assure a gall-free running characteristic with less friction.

[0028] Inset at the forward end of the cylindrical body 12 of the axial bearing 6, is a replaceable bearing plate 13. This bearing plate 13 is constructed of the same material as the bearing shell 8 and possesses, likewise, micro-openings 11, which run in an axial direction to the shaft 3.

[0029]FIG. 2 demonstrates a portion of a cross-section through the bearing surface of the bearing shell 8 with a micro-opening 11 constructed therein. The following description of the micro-opening is applicable to the micro-openings in the bearing surface of the bearing plates 13 or 32 and 26 of the axial bearing 6 or 30 and 22. On the rear side of the bearing shell, however, which border on the compressed air chambers 10, the cross-sections of the micro-openings have been widened. The diameter of the widened zones measures more than 100 mm, preferably more than 1 mm, so that the widened zone of the micro-openings can be bored with a conventional tool, i.e. can be so manufactured. The part of the micro-openings 11 which are continuous to the air gap 9 possess a cross-section of less than 100 mm and are made by a special procedure, namely boring by laser.

[0030] The diameter of the small diameter openings runs some 80 to 100 mm, preferably 20 to 50 mm. Since only that shell 8 section containing the micro-openings 11, which borders onto the air gap 9, is thin, the micro-openings 11 need be provided only in a small range of depth. The depth of the micro-opening 11 with the small cross-section can lie in the range of 50 to 3 mm. In spite of abrasion of the bearing shell 3 from the surface of the shaft 3, which occurs during long run operations, the diameter of the small cross-sectional micro-openings 11 remains constant throughout their depth, so that in spite of probable occurring wear of the bearing shell 8, the air flow through the cross-section of the narrowed micro-openings 11 permits adjustment. Because of this arrangement, the incoming air flow into the air gap 9 is very exactly determined. The same can be said in regard to the bearing plate 32 and the bearing disk 26. (see below.)

[0031]FIG. 3 shows a second embodiment for the axial bearing of the spin-rotor 1. The rotor plate 2 and the radial bearing 5 which is adjacent to the spin-rotor 1, as well as the drive with the drive belts 4 are exactly the same as depicted in FIG. 1. At the end of the shaft 3 distal from the rotor plate 2 is located an aerostatic bearing 20 assembly comprising a radial bearing 21 and a first axial bearing 22. In a recess of the radial bearing 21 is inserted a bearing shell 23, on the back surface of which are pressurized air chambers 25, which are circumferentially installed in a bearing housing 24. In a radial direction to shaft 3, are situated micro-openings 11, as previously described.

[0032] In the rear end surface of the bearing housing 24 is inserted a bearing disk 26, which is made in a corresponding manner to the bearing plate 13 or the bearing shell 8 or 23. In the bearing housing 24 are designed concentric, circularly shaped, pressurized air chambers, which are supplied with compressed air and it is from these that the micro-openings 11 in the bearing plate 26 allow pressurized air to be introduced into the air gap 28. On the rear end of the shaft 3, a ceramic disk 29, preferably a silicon carbide disk, is affixed by adhesive means. This ceramic disk 29 serves as opposition for the bearing disk 26. By means of the first axial bearing 22, an axial force acting on the shaft 3 in the direction of the rotor plate 2 is absorbed.

[0033] Opposite to the rear side of the ceramic disk 29 is placed a second axial bearing 30. The second axial bearing 30 is subjected to an axial force, which acts in the direction of the said bearing. In this way, the shaft 3 is held fast in its axial position, so that this shaft 3 cannot be axially moved. In the case of this embodiment example, the rotor plate 2 is, advantageously, releasably connected to the shaft 3, so that the rotor plate 2 can be replaced without a concomitant exchange of the shaft 3. Pressurized air, by means of micro-openings 11 in a bearing plate 32, is introduced into an air gap 31 of the second axial bearing 30. The pressurized air is supplied to the back side of the bearing plate 32 by a compressed air chamber 33.

[0034] For increasing the operational life of the spin-rotor 1, at least in the areas of the opposed surfaces, a silicon carbide coating 34 is applied onto the shaft 3 of said spin rotor. These areas are depicted in FIG. 1, and lie in the areas of the forward and rear radial bearings 5, 21. The silicon carbide coating 34 is placed opposite to the the surfaces of the bearing shell 8, 23.

[0035] In the case of the first embodiment, additionally the rear portion of the shaft 3 is coated with the silicon carbide layer. As seen in the embodiment of the second radial bearing as presented in FIG. 3, the ceramic disk 29 can be replaced by a low inertia disk, which is coated with a ceramic layer, preferably with a coating of silicon carbide. 

Claimed is:
 1. An open-end spinning apparatus with a spin-rotor (1), the shaft (3) whereof is supported by an aerostatic radial bearing (5, 21), having an air gap (9) between the radial bearing (2, 21) and the shaft (3), whereby the bearing surface (34) of the spin-rotor (1) coacts with the bearing surface (8, 23) of the radial bearing (5, 21) therein characterized, in that the bearing surface (34) of the spin-rotor (1) and/or the bearing surface (8, 23) of the radial bearing (5, 21) are manufactured from a basic material of polyimide or Aramid.
 2. An open-end spinning apparatus in accord with claim 1, therein characterized, in that the basic material contains essentially polyimide or Aramid and an additive.
 3. An open-end spinning apparatus in accord with claim 2, therein characterized, in that the polyimide or Aramid is compounded with graphite, Teflon®, and molybdenum disulfide (MoS₂) or a mixture of these.
 4. An open-end spinning apparatus in accord with claim 3, therein characterized, in that the quantity apportionment of the additive is greater than 20 %.
 5. An open-end spinning apparatus in accord with one of the foregoing claims, therein characterized, in that the bearing surface (34; 8, 23) of the radial bearing (5, 21) or the spin-rotor (1) is produced from a porous material.
 6. An open end spinning apparatus in accord with one of the foregoing claims, therein characterized, in that the bearing surface (8) contains a plurality of borings (11) for the passage of air.
 7. An open-end spinning apparatus in accord with claim 6, therein characterized, in that the borings (11) are distributed over an area.
 8. An open-end spinning apparatus in accord with claim 7, therein characterized, in that the borings (11) are placed in an axial direction and are circumferentially offset from one another.
 9. An open-end spinning apparatus in accord with claim 6, 7 or 8, therein characterized, in that at least a portion of the borings (11) are micro-openings.
 10. An open-end spinning apparatus in accord with claim 9, therein characterized, in that the cross-section of the micro-openings, at least in the area of the outlet side increases as the outlet is approached and/or at least in the area of the inlet side increases as the entry is approached.
 11. An open-end spinning apparatus in accord with one of the foregoing claims, therein characterized, in that the air entering into the air gap (9) passes through a throttling apparatus.
 12. An open-end spinning apparatus in accord with claim 11, therein characterized, in that the throttling apparatus is made of a porous material.
 13. An open-end spinning apparatus in accord with claim 11 or 12, therein characterized, in that the throttling apparatus possesses micro-openings for the adjustment of the air quantity conducted to the air gap (9).
 14. An open-end spinning apparatus in accord with claim 13, therein characterized, in that the outlet side of the micro-openings border on the air gap (9).
 15. An open-end spinning apparatus in accord with one of the foregoing claims, therein characterized, in that the two bearing surfaces (34; 9, 23) exhibit a low friction material pairing.
 16. An open-end spinning apparatus in accord with claim 15, therein characterized, in that in the case of the material pairing, one bearing surface substance possesses polyimide or Aramid and the other substance possesses a hard material or a hard material coating.
 17. An open-end spinning apparatus in accord with claim 16, therein characterized, in that the hard material is a ceramic, preferably comprised of silcon or of silicon carbide.
 18. An open-end spinning apparatus in accord with one of the foregoing claims, therein characterized, in that the shaft (3) is supported in the axial direction, at least in the direction of the end of the shaft (3) remote from the rotor plate (2), by means of an aerostatic axial bearing (6; 22, 30).
 19. An aerostaic radial bearing of a spin-rotor (1) for an open-end spinning apparatus, therein characterized, in that the bearing surface (8, 23) of the radial bearing (5, 21) is made of a material of polyimide or Aramid.
 20. An aerostatic radial bearing in accord with claim 19, therein characterized, in that the bearing surface (8, 23) is designed in conformance with one of the claims 1 to
 17. 21. A spin-rotor shaft set in aerostatic, radial bearings (3) for a spin rotor (1) of an open-end spinning apparatus, therein characterized in that the bearing surface (34) of the spin rotor (1) is made of a material of polyimide or Aramid.
 22. A spin-rotor shaft set in aerostatic, radial bearings (3) in accord with claim 21, therein characterized, in that the bearing surface (34) is designed in conformance with one of the claims 1 to
 17. 